Segmentation fault

zmunkz

I am building a neural network in PHP, and I am encountering some funny problems. I know a language like Java or C++ is better suited for this kind of application, but I have my reasons for using PHP.

Anyway, I have setup a network that needs to run for several thousand iterations. I am executing the script from the command line, and hoping to let it run, but I get the following behavior:

I enter:

zMac:~ mdz$ /usr/local/bin/php /Library/WebServer/Documents/nn/v2/bin/Network.class.php

It works, and I can track the progress in a log output file. Then a few second later, I get:

Segmentation fault
zMac:~ mdz$

And a popup informs me that php has quit unexpectedly.

Does anybody know anything about a segmentation fault, what might be causing it, and how I can fix it? I don't know a lot about php beyond the language grammar, and am not familiar with this error.

Thanks!

etully

I can't help you very much except to say that a seg fault often indicates that the OS choked and not PHP. Sounds to me like you used too much memory or something. It's also possible that your script uses some component of the OS and that component choked. There could be tons of possible solutions including:

reinstall the OS, patch the OS, or upgrade the OS
break down your code so that it's more efficient
troubleshoot your code to find out what line is executing when it faults
upgrade the external component(s) that choke
add more RAM to your computer

I'm not saying that this list is right - and it's definitely not comprehensive. I'm just saying that these are the kinds of solutions that you're going to need to look into to solve the problem. Obviously the right solution depends on the cause of the problem. (As much as I hate solving problems by adding more RAM, sometimes it's cheaper to spend $300 than to spend 6 weeks trying to make your code more efficient).

As for which external component might be the problem, obviously that depends on what your code looks like (which we can't troubleshoot in this forum). Find out if your code always stops at the same place or different lines every time. You'll probably need a sysadmin who knows how to monitor resources like (A) memory, (😎 cpu, and (C) which OS functions are being called.

Weedpacket

As etully notes, segfaults happen at a deeper level than PHP - it's the software that's running PHP is failing.

There may be bugs in the version of PHP you're using (bugs.php.net has a list of all those known), and these may or may not have been fixed.

The only segfaults I've seen that were actually caused by PHP code are those that as a result of infinite recursion caused a stack overflow. The only cure for that problem is to avoid trying to make an infinite number of function calls 🙂